Process of forming alloy materials by electroplating



Patented Aug. 29, 1933 PATENT OFFICE PROCESS OF FORMING ALLOY MATERIALS BY ELECTROPLATING Harold J. Kersten, Cincinnati, Ohio No Drawing. Application April 18, 1932 Serial No. 606,075

13 Claims. (01. 204-2) My invention relates to the formation by electrolytic means, of deposits containing more than one metal, For the purpose of an exemplary disclosure, I shall describe it in connection with the formation of a so-calledwhite gold. It is my object to make improvements in processes of forming white gold, and in particular in the formation of a white gold comprising gold and nickel which is useful in the arts and is resistant to nitric acid, and otherwise responds to the ordinary tests for gold, current in the jewelry arts.

It is a broader object of my invention to provide improvements in the art of plating alloys or metallic combinations more particularly having to do with the maintenance of electrolytic conditions necessary for the continuous production of the desired product. As applied to \the formation of a white gold which it is one of my objects to produce, my process permits the continuous deposition thereof so that deposits of any thickness desired may be built up. This is not to say, however, that my process and product are not equally useful for flash deposits employed to give a non-tarnishing coating to silverware, or the like.

Considerable difficulties face the Worker in the art of plating so-called alloys or metallic combinations. An electrolyte must be employed which comprises salts of more than one metal. Conditions must be so regulated that an alloy or metallic combination of the required composition is produced in spite of the well known tendency for certain metals to plate preferentially from a combination electrolyte. It is not ordinarily possible, as in simple electroplating, to maintain the composition of the bath constant by means of a soluble anode of the metal. On the contrary, the bath must be maintained constant, if at all, by continuous tests and additions of measured quantities of metallic'salts, or by arbitrary additions as and when the bath appears to need them. These baths not only result in considerable variation in the composition of the metallic deposits, but some baths heretofore employed for producing metallic combinations are only suitable for short time use, and then must be discarded or salvaged by chemical means.

It is an object of my invention therefore to provide means for maintaining a constant composition in an alloy plating bath, whereby not only is the bath fitted for continuous electroplating use, but also is adapted to produce deposits of constant character and composition.

These and. other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain series of process steps of which I shall now describe the 0 aforesaid exemplary embodiment.

In accordance with my preferred practice, my white gold alloy or metallic combination is plated from a bath containing, in water solution, potassium gold cyanide, to the amount of about 5 four grams of gold per litre. ,The nickel salt is nickel formate, and the bath is kept saturated with this salt. Saturation is maintained by keeping in the bottom of the cell, nickel formate crystals. This particular bath may be operated at 30 C., and at a current density of .2 amperes per square decimeter. It will be understood that these conditions and proportions may be varied if desired to give different results. A rise in the temperature seems preferentially to favor the deposit of more gold. A rise in the current density seems preferentially to favor the deposit of more nickel. An insoluble anode may be used if desired; but the goldcontent of the bath may be maintained by the use of a gold anode, or of an anode containing gold.

It will be clear from this exemplary disclosure of my invention, that several striking advantages are secured in the deposition of alloys. Discussing this disclosure in the order in which it has been made, it will be noted first that I have selected salts of the two different metals in such a way that the curves representing the rate of deposit of these metals lie more nearly together. In this way I avoid the great difiiculty heretofore experienced in alloy deposition because of the preferential rate of deposit of one of the metals. So far as I am aware, a metallic salt of formic acid, or other similar organic acids, has never been employed to provide a composite electrolyte in which the rate of deposit of such metals as nickel, copper, cobalt and the like is slowed up.

Secondly, I avoid a great many of those difficulties heretofore encountered in the electroplating of composite products, by maintaining the bath saturated with respect to one of the salts. So long as the bath remains saturated with nickel formate, as in the exemplary disclosure, the concentration of this salt in the bath will remain constant. The saturation may, of course, be maintained by keeping in the bottom of the bath, or elsewhere in contact with the electrolyte, an'excess of the salt of one of the metals. This immediately removes one of the of it which I have set forth hereinabove.

variables, and even with an insoluble anode it is a very much easier matter to maintain the bath constant as respects the other metals of the combination, by periodic additions of the "salts thereof. The necessity for these additions may, of course, be determined by tests; but since the bath remains constant as to its content of one of the salts, additions of the other may be made in proportion to the rate of deposit of the metallic alloys, or combination.

In the third place, I provide a composite electrolyte which is kept saturated with the salt of one of the metals. Hence I am enabled to maintain'its content of the other metal by employing a soluble anode containing it, which would vnot be possible otherwise.

It will be clear that my invention is not restricted to the particular exemplary embodiment It is equally applicable to the formation of alloys or metallic combinations of other metals. It may be employed in the formation of metallic combinations comprising gold, silver, or noble metals with nickel, copper, cobalt and the like, and may also be employed with other metallic combinations, whether they are far removed in the electro-motive series or not.

Having thus described my invention, what I claimas new and desire to secure by Letters Patent, is:

1. In a process of depositing metallic alloys or combinations, the step of maintaining the bath in saturated condition as respects one, of the salts.

2. In a process of depositing metallic alloys or combinations, the step of maintaining the bath in saturated condition as respects one of the salts, and'maintaining the content constant as to the other of said salts by periodic additions thereto.

3. In a process of plating a metallic'alloy or combination of metals, the steps of maintaining the content of the electrolyte by keeping it constantly saturated with a salt of one of the metals, and maintaining the content of the bath substantially constant with respect to the other of said metals by employing a soluble anode concomposite electrolyte and maintaining the concentration of said electrolyte with respect to the salt of one of said metals constant by causing said electrolyte to contact a body of the salt of said metal, whereby said electrolyte is maintained saturated with respect thereto.

5. A process of electroplating alloys of metallic combinations which comprises, selecting for the electrolyte salts of the several metals so that the deposition curves of said metals lie relatively close together, and maintaining said electrolyte in a saturated condition as respects one of said salts.

6. A process of electroplating alloys of metallic combinations which comprises selecting for the electrolyte salts of the several metals so that the deposition curves of said metals lie relatively close together, maintaining said electrolyte in a saturated condition as respects one of said salts, and replenishing the bath by additions of the other of said salts from time to time.

7. A process of electroplating alloys of metallic combinations which comprises selecting for the electrolyte salts of the several metals so that the deposition curves of said metals lie relatively close together, maintaining said electrolyte in a saturated condition as respects one of said salts, and maintaining the concentration of said bath substantially constant with respect to the other of said metals by employing a soluble anode consisting of said metal.

8. A process of electroplating a metallic alloy or combination which comprises employing an electrolyte containing an organic salt of a metal relatively high in the electro-motive series and a salt of a metal relatively lower in said electro-motive series, and keeping said bath concentrated with respect tothe first mentioned of said -salts by causing it to contact a quantity thereof in solid form.

9. A process of producing an electro-deposit comprising gold, and another metal, which includes the step of employing an organic salt of said other metal and keeping said electrolyte saturated with respect thereto.

10. A process of depositing gold. combinations which comprises employing in an electrolyte a salt of gold and an organic salt of a metal in the group including nickel, copper, cobalt, etc. and

maintaining said bath saturated with said organic salt.

11. A process of depositing gold combinations which comprises employing in an electrolyte a salt of gold and an organic salt of a metal in the group including nickel, copper, cobalt, etc., maintaining said bath saturated with said organic salt, and maintaining said bath of substantially constant content of gold by periodic additions thereto of said gold salt.

12. A process of depositing gold combinations which comprises employing in an electrolyte a salt of gold and an organic salt of a metal in the group including nickel, copper, cobalt, etc. maintaining said bath saturated with said organic salt, and maintining the concentration of gold in said bath by employing a soluble anode containing gold.

13. An electrolyte for plating a gold combination containing a salt of gold and a salt of another metal, said electrolyte saturated with said salt of the other metal.

14. An electrolyte for depositing gold combinations, said electrolyte saturated with an organic salt of a metal of the group including copper, nickel, cobalt, etc., and also containing a salt of gold.

15. An electrolyte for plating white gold which contains a gold salt and is saturated with an organic salt of nickel.

16. An electrolyte for plating alloy of gold and nickel which contains a cyanide salt of gold and a nickel formate.

17 An electrolyte for plating white gold which contains a cyanide salt of gold and anickel formate, said electrolyte being saturated with said formate.

18. An electrolyte for plating white gold which contains potassium gold cyanide substantially -in the amount of four grams of gold per litre,

and is saturated withnickel formate.

HAROLD J. KERS'IEN. 

